Magnetic gas analyzer utilizing inductive means to sense displacements and to rebalance the analyzer

ABSTRACT

Non-magnetic bodies are expelled from a zone of high flux density to zone of lower flux density in inhomogenous fields when oxygen enters the zones, the expulsion being against a very slightly biasing positioning means. A wire loop frame moves with the bodies to alter the inductive coupling between high frequency sending and receiving coils so that voltage induced in the latter varies with oxygen and concentration. The induced voltage is rectified and sent back to the loop which contains smaller loops situated in the fields so that the rectified feedback tends to urge the bodies back into the field. The regressive feedback is a measure of oxygen concentration.

[ Jan. 30, 1973 United States Patent 1 Gast 2 744 234 5/l956 Munday ctul..........................324/36 3,487,297 l2/l969Guyton................4...........,.....324/36 Primary Examiner-RobertJ. Corcoran I54] MAGNETIC GAS ANALYZER UTILIZING lNDUCTlVE MEANS TOSENSE DISPLACEMENTS AND TO REBALANCE THE ANALYZER T m d m R T m S We B.m A S H l 0 R V, e n r l m 7 A U r e B e S S a r t S g r 6 BY. km S amm r 9 0 M3 n T". 0 t n e V n l 6 7 Non- 22 Filed: Oct. 13, 1970 21 Appl.No.: 80,304

magnetic bodies are expelled from a zone of high flux density to zone oflower flux density in inhomogenous fields when oxygen enters the zones,the

[30] Foreign Application Priority Data Oct. 13,1969Germany....................P l9 5] 532.3

induced voltage is rectified and sent back to the loop which containssmaller loops situated in the fields so 56 R d that the rectifiedfeedback tends to urge the bodies 1 e erences I e back into the field.The regressive feedback is a mea- UNITED STATES PATENTS sure of oxygenconcentration.

2,700,739 1/1955 Orlando 22 Claims, 4 Drawing Figures PATENTEDJAH3019753.714.557 SHEET 10F 2 Fig.1

grwc/wtm THEODQR GAST P/ IE mI-anao I975 3.714.557

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l Flgl bej ees MAGNETIC GAS ANALYZER UTILIZING INDUCTIVE MEANS TO SENSEDISPLACEMENTS AND TO REBALANCE TI-IE ANALYZER PRIOR ART It has long beenknown to utilize in gas analyzers the characteristic that in the sameinhomogenous magnetic field a material with a greater magneticsusceptibility will migrate to locations of greater flux density and thematerial with the lower susceptibility to the region of lower fieldstrength. This action is therefore suitable in gas analysis because afew gases exhibit a distinguishing susceptibility. Oxygen e. g. has asusceptibility much greater than almost all the other gases, and so itis possible to manufacture a sensitive oxygen analyzer specific foroxygen.

In one conventional form of analyzer shown in German Pat. No. 947,932,there is a dumb-bell shaped expellable piece that carries at its twoends ball-shaped thickenings between the pole pieces of two U-shapedpermanent magnets set opposite each other. The pole pieces are formed sothat the magnetic field is inhomogenous and the whole arrangement issituated in a gas mixture from which the admitted components withdifferent susceptibilities are to be determined. During the measurementfor oxygen the oxygen molecules, due to their great susceptibility,preferentially enter the location of high flux density and expeltherefrom nonmagnetic glass end pieces or the dumb-bell. When thedumb-bell is mounted to to turn about its transverse axis against arestoring force, the angle of turn is a measure of the proportion byvolume of oxygen in the throughput gas.

Its also known to mount the dumbbell shaped expellable body on a wireloop. It is then possible to provide a mirror to move with theexpellable body so that rays from a light source falls on the mirror andare reflected to a photo-electric cell to produce a current proportionto the deflection, which is fed back to the loop, after amplification ifnecessary, to oppose the tendency of the loop to turn. Thus the feedbackor compensating current is a measure of the volumetric content of themagnetic gas in the sample.

Among the drawbacks to such a device was the fact that the light on themirror must come from the outside and this presented many difficultieswhen the whole arrangement had to be situated in a gas-tight housing.Also the energy fed back from a sufficiently accurate photo-electriccell had to be produced and then amplified.

The invention has as its object a pickup or sensing of the deviation ofthe turning of such a loop mentioned and to provide the necessarycompensation current by purely electrical means and providing an oxygenanalyzer with fully automatic compensation and greater accuracy.

SUMMARY OF THE INVENTION The invention is a device for the determinationof magnetic gas especially oxygen concentration in a sample of gashaving a deflectable or turnable wire loop or frame element providedwith non-magnetic end pieces situated in the inhomogenous field zonesbetween the poles of two magnets. The presence of a magnetic gas tendsto expel the two end pieces and turn the loop. In

. the device, a tendency toward deviation by turning sets up acompensating current flow in a means and tends to restore the loop tooriginal position. Thus far the device is conventional; the novelty ofthe invention is in the combination of the preceding elements with anexciter or sending coil system fed by an oscillator, a receiver coilsystem, inductive coupling between the two systems being accomplished atleast in part by way of the wire loop or frame carrying the non-magneticend pieces.

It is advantageous to have the non-magnetic end pieces lie in anequatorial or horizontal plane, that is to say, a plane to which theflux lines of the magnet pole are perpendicular and remainder of theframe or loop constitute a coupling means, turnable about an axisperpendicular to the plane, between the two coil systems.

It is further advantageous that the loop or frame composes part of adeflectable system having two ends in a position to develop a magneticfield to coact with the inhomogenous field when a current flows in theloop and so enable compensation for deflection of the loop and at thesametime have a portion of the frame act as coupling means between thecoil systems.

The deflectable frame is mounted between tension strips which provideleads to the frame for compensation current. The frame may be consideredas having two sides and current flows through each side of the frame incounter directions, that is, the frame as a whole develops no field.Indeed a homogenous field is produced without influence from the outsideon the deflectable frame, since the action of the compensating currentin both the vertical and horizontal parts of the frame cancels out eachother.

DRAWING FIG. 1 schematically shows a form of the invention with twopossible means for the exciter coil system.

FIG. 2 shows circuitry for the invention with symbolic block forms aselements.

FIG. 3 shows a practical example of the circuitry in FIG. 2.

FIG. 4 is a graph showing the linearity of the relationship betweencompensation current or millevolts and deflection.

DESCRIPTION OF PREFERRED EMBODIMENTS Basically the force F tending toexpel a non-magnetic body from an inhomogeneous field where oxygen ispresent may be expressed by the following where H is the magnetic fieldstrength S is the displacement in the direction of the gradient of fieldstrength V is the volume of the non-magnetic body, and

K is the susceptibility of the oxygen content in the mixture to beanalyzed.

The force experienced on the non-magnetic body is proportional to thesusceptibility of the gas mixture and hence, in practice proportional tothe partial mass or pressure of oxygen in the gas mixture, since thesusceptibilities of almost all other gases in the mixture are smallenough to be disregarded. In the embodiment as shown in FIG. 1, thenon-magnetic body in which the force is exerted comprises two glassspheres and 5. These spheres can be hollow and vacuous or filled with agas of known composition. The spheres are mounted fast on a torsionbalance beam 6, preferably on a part integral therewith, the beam beingas a wire frame with their horizontal projections as at 7 and 7 turnedabout 90 and embrasing the spheres equatorially.

The deflectable element or frame is suitably mounted by means of tensionstrips 8 and 8' so that the spheres are situated in inhomogenousmagnetic fields between legs of two U-shaped permanent magnets 1 and 2,and 3 and 4 respectively having leveled end pole pieces 1, 2', 3' and4'. The levels leave the gap between pieces 1 and 2' widening toward therear and the gap between pieces 3' and 4 widening toward the front asshown in the drawing. Hence an inhomogenous field exits between bothpairs of pole pieces. This means that the flux density between polepieces 1' and 2 decreases from front to rear on the right in the drawingand from rear to front between pieces 3' and 4' on the left. When thenon-magnetic spheres 5 and 5' are situated in the inhomogenous fields noforce tends to move them horizontally as long as nothing is drawn intothe spaces between the pole pieces to displace the bodies. However if amagnetic gas enters the vicinity of the spaces, the gas willpreferentially be drawn into the zone of greater flux density andproportionally to the density of the flux to tend to expel the glassspheres. Due to the mirror image construction at the left and right ofthe magnet pairs a two-fold torque is exerted on the frame due to theexpulsion force directions being in opposite directions.

The whole arrangement thus far described is enclosed in a gas-tighthousing 9, outlined by dashed lines, provided with inlet and outletmeans and 10'. If gas having an oxygen content enters, the oxygenbecomes correspondingly drawn into the zones of highest flux density anddisplaces the glass spheres and exerts a corresponding torque againstthe tension strips.

The entire balance beam is developed as a short circuit loop ofelectrically conductive material such as copper wire and includes aspreviously mentioned,'two laterally projecting loops turned 90 withrespect to the main flat plane of the frame for carrying the spheres.

According to the shown example of the invention a fixed cylindricalexciter transmitter or sending coil 12 is disposed so as to lie with itsaxis perpendicular to general location of the plane of the frame 6 andintersect it at or near the mid point of the area included by the frame.The coil 12 may be within the frame 6 or it may be in a recess inhousing 9 where it can be closed off from the effect of corrosive gas.Coil 12 has flowing in it a high frequency current as from an externaloscillator (See FIGS. 2 or 3), and as a result a high frequency voltageis induced in the wire frame 6. The value and phase of the inducedvoltage is dependent only to a negligable degree on the angular positionof the frame relative to the coil 12 especially because the frame turnsonly on the order of 1.

Instead of having the fixed sending coil at the middle of the wire frame6 there can be, for example, two separate coils l4 situated parallel toeach other under the wire frame. The two coils 14 can be connected inseries or parallel for being fed by an oscillator similar tooscillatorlS. A high frequency voltage can be induced to the .wire frameor balance beam 6 by either coil 12 or 14.

In a different location, one or more coils 15 may be situated say, abovethe wire frame either inside or outside the housing 9 with the axis ofthe coil 15 lying perpendicular in space to that of the axis oftransmitting or exciter coils shown at 12 or 14, and with this relativeangular disposition there is absolutely no inductive coupling directlybetween the two coils 15 and 12 or 14. Coils shown as 15 serve as pickupor receiving coils and each is so disposed that a voltage is induced ineither one or the pair by way of the wire frame 6, the voltage dependingin magnitude and phase strictly linearly with the deviation by turningof the wire frame. Thus the magnitude and phase of the induced highfrequency voltage in the coil or coils 15 is a measure of deflection ofthe wire frame 6. (See FIG. 3).

If the receiver coils of the pair 15 have their axes in the plane of theshort circuit frame 6, they are inductively coupled to the coil 12 or 14exclusively by the short circuit frame 6 when the latter is deflected.

As shown in H6. 2, the output voltage from coil 15 is suitably led to anamplifier 16, preferably one of the socalled resistor capacitor feedback type with high amplification, the amplified output going to a phasecorrecting DC rectifier 17 from which a rectified output can be measuredas a direct current. This direct current varies in direction with thedirection of deflection of the frame 6 and the magnitude of the currentvaries proportionally with the degree of deflection. This current, whichis a measure of the oxygen content of the gas sample within the housing9, is suitably fed by means of the tension strips 8 and 8' to thebalance beam, with rectified polarity, so that a force appears at thetwo projecting loops 7 and 7 surrounding the glass spheres 5 and 5'.This force, assuming proper polarity of the current, operates in thedirection of graduation of the inhomogenous field strength. Since thecurrent led to the frame 6 divides at the point of mounting the frame onthe respective tension strips it flows in the two conductive projectingloops 7 and 7 situated between the respective pole pieces to produce apair of forces. By having the proper polarity of the pole pieces thispair of forces is such that they form a couple to operate counter to thenormal forces tending to push the glass spheres out from between thepole pieces when a magnetic gas is present. In this way the netdeflection of the frame is made very small with only enough deviation tomaintain the regressive current.

The system just described is a so-called torque compensation thatcorresponds somewhat to a torsion balance. The couple of forces to becompensated produces a torque which makes the deflection regressiveuntil a quite negligible residual displacement or angle is obtained,which is necessary in order to produce the current used for thecompensation. The requisite current for the compensation is a measure ofthe torque or force which acts counter to the expelling force on theglass spheres and therefore volumetric proportion of the gas to bemeasured. An indicating instrument interposed in the current path of thecompensation current can be calibrated for volume percent of the gaspresent.

Other means may be used for energizing the frame, for example, the framemay have d.c. connection to the source of energizing current, or frame 6may be energized by induction through a solonoidal coil going throughthe center of the wire frame. Also, as already mentioned, a second pairof rectangular shaped coils 14, can be used for energizing frame 6 turnsof such coils 14 are arranged parallel to the wire frame 6. The couplingmay be increased by the use of iron or soft steel cores in thestationary coils.

The receiving or pickup coils can be connected in series or parallel butare so chosen in polarity that the signal induced in them by turning ofthe moving parts becomes amplified; Coils 15 are also connected to theexterior via a parallel connected capacitor, as shown in FIG. 3, havingresonant frequency with the oscillator. A frequency of about 470 kHzgives satisfactory resonance.

FIG. 2 shows only in block fashion the assemblies shown in FIG. 3. Theoscillator is made up of two transistors whose emitters circuits areconnected together and is completely separated conductively from theremainder of the combination up to the conductors 18 which lead to thephase correcting rectifier. The transfer of signals from the sendingcoil 12 or 14 to the receiver coil 15 results exclusive by the positionof the frame'6 as shown only schematically in FIGS. 2 and 3 and whosedeflection is shown exaggerated.

The input signal passed on to the receiver coil 15 is further amplifiedby a two stage amplifier and the led to a phase correcting rectifier.This can, for example, be accomplished by a middle-tap transformer 19.Since the several component parts are self-evident further descriptionis unnecessary: it is noted however that the output signal of therectifier is preferably amplified by a DC amplifier with feedback.

In each case the compensation current flowing in the wire frame 6maintains a predetermined orientation of the wire frame with its twoglass spheres 5 and 5', nearly independent of the momentary prevailingoxygen concentration in the gas mixture to be analyzed.

It should however be noted that feed voltages are stabilized, in orderthat no inaccuracies occur due to unexpected variation in the oscillatorvoltage or in the amplification factors.

A further special advantage in forming the frame as a short circuit ringis that the D. C. flows in both halves somewhat relative to theprojecting loops 7 and 7, so that due to the compensating current themoments acting on the glass sphere are equalized out in the same planeand location so there is no reaction force on the tension mountingstrips. Moreover the invention is completely unaffected by stray outerhomogenous magnetic fields from any direction, since the current flow ismagnetically counter to each other in the two halves of the wire frame6. This is true of the vertical parts of the frame as well as of thehorizontal parts. Lateral movement of the expelled system i. e. the wireframe with the two sphere does not affect the null point or sensitivity.

Moreover, instead of the separate oscillator and subsequent amplifierfor the induced voltage it is possible to employ a self-oscillatoryamplifier and of course of such sign that the coils l5 and 14 influencedby their coupling due to the balance beam have self oscillatoryfeedback. The limitation on oscillation for such an amplifier can bechosen so precisely that a mere turning of the balance beam system issufficient to start oscillation. The oscillator voltage becomesrectified and fed back to the wire frame 6 for compensating effect. Hereagain the compensation current is a measure of the oxygen content in thesample gas. An advantage of this arrangement is that no sort of voltagestabilizer is necessary for the oscillator.

The invention claimed is:

1. In a magnetic gas analyzer wherein at least one nonmagnetic body isdisposed on a deflectible carrier and being situated in an inhomogenousmagnetic field, tending to become expelled and deflected from zones ofgreater magnetic flux density of the field with increasing concentrationof a magnetic gas in the region of the field, and wherein a compensationcurrent in the carrier produces a counter force tending to restore thedeflected body to its undefiected position occupied prior to theincrease of said concentration as the compensation current flows throughthe carrier for the body, the carrier upon deflection turning on anaxis, the improvement comprising a stationary transmitting coil means;

stationary receiving coil means disposed in particular relation to thetransmitting coil means;

the carrier including a wire frame loop, extending in a plane thatincludes said axis and being disposed in relation to the transmittingand the receiving coil means for inductive coupling to the transmittingcoil means and further for inductive coupling with the receiving coilmeans upon induction of current in the loop by the transmitting coilmeans and in dependence upon the relative angular position of the wireframe loop, the angular disposition of the wire frame loop beingdetermined by deflection of said body and by the tendency to restoresaid body to said undefiected position;

first means connected for feeding an oscillating current to thetransmitting coil means; and

second means connected to said receiving coil means for derivingtherefrom a signal representing the deflection of said frame loop andfurther connected for providing said compensating current in responsethereto and feeding said compensating current to said carrier.

2. An analyzer as claimed in claim 1, wherein the carrier is symmetricto said axis and is provided with lateraly projecting loops, each loopcarrying one body, the loops being situated in two such inhomogenousfields, and two U-shaped magnets having pole ends of one opposite poleend of the other to form the two fields therebetween.

3. An'analyzer as claimed in claim 2, the projecting loops of thecarrier lying in a plane transverse to said axis and to the plane ofsaid frame loop, the flux lines'of the fields being perpendicular to theplane of the projecting loops, the frame loop of the carrierelectrically connected to the projecting loops.

4. An analyzer as claimed in claim 3 and tension strip means formounting the frame loop respectively at its sides, and the projectingfor carrying compensating current to the frame and loops therein andpermitting deflection of the frame about said vertical axis.

5. An analyzer as claimed in claim 3, the transmitting coil meansincluding first and second interconnected coils the turns of the coilsbeing substantially in planes parallel to that of the frame loop.

6. An analyzer as claimed in claim 3, the receiving coil means includingfirst and second interconnected coils, the planes of turns of thereceiving coils being substantially perpendicular to the plane of theframe loop.

7. An analyzer as claimed in claim 4 the second means including anamplifier connected to the receiving coil means for amplifying thevoltage induced therein, and a phase correcting rectifier connected tothe amplifier for rectifying the amplifier output, the output of therectifier being connected to the two respective tension strips forsupplying compensating current to the loops.

8. An analyzer as claimed in claim 4, said transmitting coil being asolonoidal coil in the middle of the frame.

9. An analyzer as claimed in claim 4, and a housing about the saidmagnets, frame and strips, the receiving coil means being outer of thehousing, the turns of the receiving and transmitting coil means beingsubstantially in mutually perpendicular planes.

10. In combination with an analyzer as claimed in claim 4, a housingaround such analyzer, inlet and outlet means for passage of gas throughthe housing, the direction of travel of the gas through the housingbeing generally perpendicular to said turning axis of said frame.

11. An analyzer as claimed in claim 4 wherein the means for supplyingthe oscillating current to the sending coil is a self oscillatoryamplifier and the sending and receiving coils are connected into thefeedback circuit of the self oscillating amplifier whose rectifiedoscillatory signal output is connected to the wire frame.

12. Gas analyzer as in claim 1, wherein each of the transmitter andreceiving coil means includes at least one coil having turns, andwherein the frame loop is disposed in a plane substantially parallel tothe turns of the transmitter coil means, the turns of the coil of thereceiving coil means being substantially perpendicular to the plane ofthe frame loop.

13. Gas analyzer as in claim 12, wherein a pair of bodies is disposed onthe carrier and symmetrically to the axis, the frame loop being providedadditionally with two projecting loops oriented in a plane transverse tothe frame loop plane and respectively enveloping said bodies of thepair, the frame loop connected to said second means so that half of thecompensating current flows through half of the frame loop at one side ofthe axis and through one projecting loop, and the other half of thecompensating current flows through the other half of the frame loop andthrough the other projecting loop.

14. In a magnetic gas analyzer having at least one nonmagnetic body, thecombination, a carrier for the body and mounted for providing deflectionrelative to an axis and including a wire loop extending in a plane thatincludes said axis;

means establishing an inhomogeneous magnetic field and effective on thebody so that the body deflects 6 means for providing an oscillatorymagnetic field having a magnetic axis and disposed for energizing saidwire loop and for inducing current flow therein;

inductive pickup means having a magnetic axis and disposed so that themagnetic axis runs parallel to said deflection axis, for picking upmagnetic flux from the wire loop as resulting from the induced currentflow in the wire loop, the picked up flux depending on the angularposition of the wire loop in relation to said deflection axis, thepickup means providing signals representing said picked up flux; and

electric circuit means connected to the pickup means to be responsive tothe signals developed in the pickup means as resulting from said pickedup magnetic flux, and providing a dc. current to the carrier independence upon the picked up signals to be effective adjacent said bodyfor counteracting said deflection as resulting from said expelling.

15. In an analyzer as in claim 14, wherein said carrier includes asecond loop extending from said wire loop and in a plane transverse tothe plane of said wire loop, said second loop enveloping said body andproviding a magnetic field effective in and superimposed upon saidinhomogeneous field in response to the current in the carrier. I

16. In an analyzer as in claim 14, and having two nonmagnetic bodieswherein the carrier includes a pair of relatively small loops extendingfrom said wire loop and in a plane transverse to the plane of-said wireloop, said small loops enveloping said bodies and respectively providingmagnetic fields effective in and superimposed upon said pair ofinhomogeneous magnetic fields, and together counteracting saiddeflection resulting from the expelling of the bodies by the magneticgas in each said fields, the dc. current being fed into said wire loopfor flow through said small loops and being magnetically ineffective asto inductive coupling of the wire loop to the pickup means.

17. In an analyzer as in claim 16, said pickup means including a pair ofcoils disposed symmetrically to said axis adjacent said wire loop andeach with a magnetic axis parallel to said deflection axis.

18. In an analyzer as in claim 16, wherein said wire loop extends in aplane transverse to the magnetic axis of the means for providing anoscillatory magnetic field.

19. In an anzlyser as in claim 14, wherein said wire loop extends in aplane transverse to the magnetic axis of the means for providing anoscillatory magnetic field.

20. In a magnetic gas analyzer having a pair of nonmagnetic bodies,further having means to establish two inhomogeneous magnetic fields;

a carrier for suspending said pair of bodies for rotation on an axis andrespectively in the two fields, the fields effective on the bodies sothat they deflect in similar rotational directions on said axis inresponse to a magnetic gas tending to accumulate in zones of greatermagnetic flux density thereby expelling said bodies;

the carrier including a short circuited frame loop extending in a planethat includes said axis, further including a pair of projecting loopssymmetrically integral with said frame loop, said projecting loopsextending in planes transverse to the plane of the frame loop, theprojecting loops respectively extending around said bodies;

means including at least one transmitter coil and disposed for inducingcurrent in the frame loop which, when flowing through the projectingloops, produces self-compensating, oppositely directed magneticinteraction with said inhomogeneous fields not causing deflection of theframe; pickup means, including at least one coil and inductivelyresponsive to deflections of the frame loop about said axis; and

circuit means connected to the pickup means and providing a d.c. currentrepresentative of said response of said pickup means, and feeding saidd.c. current to said frame loop thereof, to be effective in the twoprojecting loops, for similarly directed interaction with theinhomogeneous magnetic fields tending to restore undeflected position ofthe two bodies as suspended by the carrier.

21. In an analyzer as in claim 20, wherein suspension means for theframe loop suspends the frame loop in said axis and at opposite ends ofsaid frame loop, said d.c. current being fed into the frame loop throughthe suspension means, the d.c. current branching into first and secondportions to flow in opposite directions through the frame loop portionsin relation to the axis, the first and second portions respectivelyflowing through the projecting loops.

22. In an analyzer as in claim 21, wherein the pickup means include apair of coils each having magnetic axis parallel to the axis of saidcarrier, and respectively disposed in the vicinity of said frame loopportions on one and the other side of said axis of said carrier.

III i t t i

1. In a magnetic gas analyzer wherein at least one nonmagnetic body isdisposed on a deflectible carrier and being situated in an inhomogenousmagnetic field, tending to become expelled and deflected from zones ofgreater magnetic flux density of the field with increasing concentrationof a magnetic gas in the region of the field, and wherein a compensationcurrent in the carrier produces a counter force tending to restore thedeflected body to its undeflected position occupied prior to theincrease of said concentration as the compensation current flows throughthe carrier for the body, the carrier upon deflection turning on anaxis, the improvement comprising a stationary transmitting coil means;stationary receiving coil means disposed in particular relation to thetransmitting coil means; the carrier including a wire frame loop,extending in a plane that includes said axis and being disposed inrelation to the transmitting and the receiving coil means for inductivecoupling to the transmitting coil means and further for inductivecoupling with the receiving coil means upon induction of current in theloop by the transmitting coil means and in dependence upon the relativeangular position of the wire frame loop, the angular disposition of thewire frame loop being determined by deflection of said body and by thetendency to restore said body to said undeflected position; first meansconnected for feeding an oscillating current to the transmitting coilmeans; and second means connected to said receiving coil means forderiving therefrom a signal representing the deflection of said frameloop and further connected for providing said compensating current inresponse thereto and feeding said compensating current to saidcarrier.
 1. In a magnetic gas analyzer wherein at least one nonmagneticbody is disposed on a deflectible carrier and being situated in aninhomogenous magnetic field, tending to become expelled and deflectedfrom zones of greater magnetic flux density of the field with increasingconcentration of a magnetic gas in the region of the field, and whereina compensation current in the carrier produces a counter force tendingto restore the deflected body to its undeflected position occupied priorto the increase of said concentration as the compensation current flowsthrough the carrier for the body, the carrier upon deflection turning onan axis, the improvement comprising a stationary transmitting coilmeans; stationary receiving coil means disposed in particular relationto the transmitting coil means; the carrier including a wire frame loop,extending in a plane that includes said axis and being disposed inrelation to the transmitting and the receiving coil means for inductivecoupling to the transmitting coil means and further for inductivecoupling with the receiving coil means upon induction of current in theloop by the transmitting coil means and in dependence upon the relativeangular position of the wire frame loop, the angular disposition of thewire frame loop being determined by deflection of said body and by thetendency to restore said body to said undeflected position; first meansconnected for feeding an oscillating current to the transmitting coilmeans; and second means connected to said receiving coil means forderiving therefrom a signal representing the deflection of said frameloop and further connected for providing said compensating current inresponse thereto and feeding said compensating current to said carrier.2. An analyzer as claimed in claim 1, wherein the carrier is symmetricto said axis and is provided with lateraly projecting loops, each loopcarrying one body, the loops being situated in two such inhomogenousfields, and two U-shaped magnets having pole ends of one opposite poleend of the other to form the two fields therebetween.
 3. An analyzer asclaimed in claim 2, the projecting loops of the carrier lying in a planetransverse to said axis and to the plane of said frame loop, the fluxlines of the fields being perpendicular to the plane of the projectingloops, the frame loop of the carrier electrically connected to theprojecting loops.
 4. An analyzer as claimed in claim 3 and tension stripmeans for mounting the frame loop respectively at its sides, and theprojecting for carrying compensating current to the frame and loopstherein and permitting deflection of the frame about said vertical axis.5. An analyzer as claimed in claim 3, the transmitting coil meansincluding first and second interconnected coils the turns of the coilsbeing substantially in planes parallel to that of the frame loop.
 6. Ananalyzer as claimed in claim 3, the receiving coil means including firstand second interconnected coils, the planes of turns of the receivingcoils being substantially perpendicular to the plane of the frame loop.7. An analyzer as claimed in claim 4 the second means including anamplifier connected to the receiving coil means for amplifying thevoltage induced therein, and a phase correcting rectifier connected tothe amplifier for rectifying the amplifier output, the output of therectifier being connected to the two respective tension strips forsupplying compensating current to the loops.
 8. An analyzer as claimedin claim 4, said transmitting coil being a solonoidal coil in the middleof the frame.
 9. An analyzer as claimed in claim 4, and a housing aboutthe said magnets, frame and strips, the receiving coil means being outerof the housing, the turns of the receiving and transmitting coil meansbeing substantially in mutually perpendicular planes.
 10. In combinationwith an analyzer as claimed in claim 4, a housing around such analyzer,inlet and outlet means for passage of gas through the housing, thedirection of travel of the gas through the housing being generallyperpendicular to said turning axis of said frame.
 11. An analyzer asclaimed in claim 4 wherein the means for supplying the oscillatingcurrent to the sending coil is a self oscillatory amplifier and thesending and receiving coils are connected into the feedback circuit ofthe self oscillating amplifier whose rectified oscillatory signal outputis connected to the wire frame.
 12. Gas analyzer as in claim 1, whereineach of the transmitter and receiving coil means includes at least onecoil having turns, and wherein the frame loop is disposed in a planesubstantially parallel to the turns of the transmitter coil means, theturns of the coil of the receiving coil means being substantiallyperpendicular to the plane of the frame loop.
 13. Gas analyzer as inclaim 12, wherein a pair of bodies is disposed on the carrier andsymmetrically to the axis, the frame loop being provided additionallywith two projecting loops oriented in a plane transverse to the frameloop plane and respectively enveloping said bodies of the pair, theframe loop connected to said second means so that half of thecompensating current flows through half of the frame loop at one side ofthe axis and through one projecting loop, and the other half of thecompensating current flows through the other half of the frame loop andthrough the other projecting loop.
 14. In a magnetic gas analyzer havingat least one nonmagnetic body, the combination, a carrier for the bodyand mounted for providing deflection relative to an axis and including awire loop extending in a plane that includes said axis; meansestablishing an inhomogeneous magnetic field and effective on the bodyso that the body deflects the carrier on the axis in response to amagnetic gas tending to accumulate in zones of greater magnetic fluxdensity thereby expelling said body; means for providing an oscillatOrymagnetic field having a magnetic axis and disposed for energizing saidwire loop and for inducing current flow therein; inductive pickup meanshaving a magnetic axis and disposed so that the magnetic axis runsparallel to said deflection axis, for picking up magnetic flux from thewire loop as resulting from the induced current flow in the wire loop,the picked up flux depending on the angular position of the wire loop inrelation to said deflection axis, the pickup means providing signalsrepresenting said picked up flux; and electric circuit means connectedto the pickup means to be responsive to the signals developed in thepickup means as resulting from said picked up magnetic flux, andproviding a d.c. current to the carrier in dependence upon the picked upsignals to be effective adjacent said body for counteracting saiddeflection as resulting from said expelling.
 15. In an analyzer as inclaim 14, wherein said carrier includes a second loop extending fromsaid wire loop and in a plane transverse to the plane of said wire loop,said second loop enveloping said body and providing a magnetic fieldeffective in and superimposed upon said inhomogeneous field in responseto the current in the carrier.
 16. In an analyzer as in claim 14, andhaving two nonmagnetic bodies wherein the carrier includes a pair ofrelatively small loops extending from said wire loop and in a planetransverse to the plane of said wire loop, said small loops envelopingsaid bodies and respectively providing magnetic fields effective in andsuperimposed upon said pair of inhomogeneous magnetic fields, andtogether counteracting said deflection resulting from the expelling ofthe bodies by the magnetic gas in each said fields, the d.c. currentbeing fed into said wire loop for flow through said small loops andbeing magnetically ineffective as to inductive coupling of the wire loopto the pickup means.
 17. In an analyzer as in claim 16, said pickupmeans including a pair of coils disposed symmetrically to said axisadjacent said wire loop and each with a magnetic axis parallel to saiddeflection axis.
 18. In an analyzer as in claim 16, wherein said wireloop extends in a plane transverse to the magnetic axis of the means forproviding an oscillatory magnetic field.
 19. In an anzlyser as in claim14, wherein said wire loop extends in a plane transverse to the magneticaxis of the means for providing an oscillatory magnetic field.
 20. In amagnetic gas analyzer having a pair of nonmagnetic bodies, furtherhaving means to establish two inhomogeneous magnetic fields; a carrierfor suspending said pair of bodies for rotation on an axis andrespectively in the two fields, the fields effective on the bodies sothat they deflect in similar rotational directions on said axis inresponse to a magnetic gas tending to accumulate in zones of greatermagnetic flux density thereby expelling said bodies; the carrierincluding a short circuited frame loop extending in a plane thatincludes said axis, further including a pair of projecting loopssymmetrically disposed to said axis and extending from and beingintegral with said frame loop, said projecting loops extending in planestransverse to the plane of the frame loop, the projecting loopsrespectively extending around said bodies; means including at least onetransmitter coil and disposed for inducing current in the frame loopwhich, when flowing through the projecting loops, producesself-compensating, oppositely directed magnetic interaction with saidinhomogeneous fields not causing deflection of the frame; pickup means,including at least one coil and inductively responsive to deflections ofthe frame loop about said axis; and circuit means connected to thepickup means and providing a d.c. current representative of saidresponse of said pickup means, and feeding said d.c. current to saidframe loop thereof, to be effective in the two projecting loops forsimilarly directed interaction with the inhomogeneous magnetic fieldstending to restore undeflected position of the two bodies as suspendedby the carrier.
 21. In an analyzer as in claim 20, wherein suspensionmeans for the frame loop suspends the frame loop in said axis and atopposite ends of said frame loop, said d.c. current being fed into theframe loop through the suspension means, the d.c. current branching intofirst and second portions to flow in opposite directions through theframe loop portions in relation to the axis, the first and secondportions respectively flowing through the projecting loops.